Ben discovers Tucker has been making extra cash by visiting a sperm bank. In order to help Tucker pick up a nurse at the bank, Ben agrees to donate his own sperm but quickly regrets his decision after a couple chooses his sample. Riley and Danny continue to fight while attempting to host their friend's engagement party. Their moms, archenemies Bonnie and Jennifer, team up to get Riley and Danny back together.

Baby Daddy follows Ben, a young man in his early 20s living the life of a bachelor in New York City with his buddy, Tucker, and his brother, Danny. Their lives are turned upside down when they come home one day to find a baby girl left on the doorstep by an ex-girlfriend of Ben's. After much deliberation, Ben decides to raise the baby with the help of his friends and his protective and sometimes over-bearing mother, Bonnie, and his close female friend, Riley.